#include <sfx/passwd.hxx>


....

String aPwdTitle( RTL_CONSTASCII_USTRINGPARAM( "Document password" ) );
SfxPasswdDialog aDlg( this, &aPwdTitle );
aDlg.ShowExtras( SHOWEXTRAS_CONFIRM );

String aPassword, aConfirm;
bool bCanceled = false;
do
{
    bCanceled = (aDlg.Execute() != 0);
    if( ! bCanceled )
    {
        // dialog was not canceled
        aPassword = aDlg.GetPassword();
        aConfirm = aDlg.GetConfirm();
        
        if( ! aPassword.Len() )
        {
            ErrorBox aBox( this, String( RTL_CONSTASCII_USTRINGPARAM( "password empty" ) ) );
            aBox.Execute();
        }
        else if( aPassword != aConfirm )
        {
            ErrorBox.aBox( this, String( RTL_CONSTASCII_USTRINGPARAM( "password not confirmed" ) ) );
            aBox.Execute();
        }
    }
} while( !bCanceled && aPassword != aConfirm );

if( ! bCanceled )
{
    // set new password here
}